Environmental Purity Can Cost Too Much MARTIN FELDSTEIN and KATHLEEN FELDSTEIN, Martin Feldstein is a former chairman of the presidential Council of Economic Advisers. His wife, Kathleen Feldstein, is an economist

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U.S. Stake in East Bloc Is Limited LAURA D'ANDREA TYSON, LAURA D'ANDREA TYSON is professor of economics at the University of California, Berkeley, and research director of the Berkeley Roundtable on the International Economy